A Bottle Cap Worth of Water Can Breed Several Hundred Mosquitoes...
Mosquitoes reproduce in as little as two tablespoons of water and under ideal breeding conditions that small amount of water only needs to exist for a mere 5 days for adult mosquitoes to develop.
Source: University of Illinois.
Debra Hagstrom
University of Illinois


A bottle cap worth of water can wreak havoc on your yard
A few unchecked spots can turn your yard into a mosquito farm

Most people get the obvious standing water issues...
More...
Every customer tells me they know about standing water.
But I still find enough water in the yard to make it a mosquito paradise.
If you don't know where the mosquitoes are coming from... your yard could be the culprit
In a big backyard, all of these containers can be tricky to identify by humans, but mosquitoes don't have any trouble finding them...
Source: Pest Control Technology.
Laura Straub
Pest Control Technology

Even if you don't see any standing water... items that could hold water can hide mosquito eggs waiting to hatch.
You need to scrub down these troubled spots (or even better... remove them from your yard).
Container mosquitoes lay their eggs along the water line inside of these unconventional containers, and eggs exist in a dry, suspended state for as long as a year.
Source: Center for Disease Control.
Center for Disease Control


Mosquito eggs can hide in dry areas until moisture returns
Top Mosquito Hot Spots People Miss In Their Yard
Piles of Leaves

Moisture from leaf piles are great places for mosquitoes to lay eggs
Leaf litter and debris... provides nutrition for the larvae.
Source: Environmental Protection Agency.
Environmental Protection Agency
Leaf piles maintain moisture... which leads to mosquito eggs...
Solutions:
Uncovered Garbage Cans

People usually miss these as they aren't checking storage areas...
Trash cans full of water breeding thousands of mosquitoes can turn your yard into a nightmare. I usually find these on the side of the house where no one's been in a while.
Out of sight, out of mind doesn't work here... mosquitoes still find them.
Solutions:

Go for the lid solution if your unused trash can still holds water upside down
Wrong Way Splash Block

Here is an example of a splash block placed the wrong way.
Splash block turned the wrong way can create muddy areas (perfect for mosquito breeding).
Sometimes they can even hold water long enough to breed mosquitoes.
Solutions:
This reddit post discussed how even home inspectors frequently get this wrong.
One home inspector shared his guide on proper down spout strategies.
Ideally though you want the water as far away as possible from your foundation... that's where downspout extensions, splash guards, and a rain activated extension bag come into play.
Source: @NYHomeInspector.
Kelvin Liriano
Three Keys Home Inspections

Tire Swings (and other tires)
Wind helps rain sneak into some unexpected areas...
This makes tires an easy place for water to collect unnoticed.
Drill holes in tires in play equipment or other tire sculptures to allow water drainage and prevent future water accumulation.
Source: Environmental Protection Agency.
Environmental Protection Agency

Drilling holes in tire swings can help prevent them from becoming mosquito hatcheries
Solutions:
Plant Saucers

Plant saucers catch water that drains from your potted plants...
Unfortunately, sometimes these saucers can hold water long enough to breed mosquitoes...
Solutions:
Bird Baths
Bird baths are a great way to attract your feathered friends to your yard...
But if the water isn't changed every few days, they'll also attract mosquitoes...

Empty bird baths before leaving town if you don’t want to come home to a yard full of mosquitoes
Solutions:
Toys & Garden Tools
If you have kids or an avid gardener in your family...
Toys or garden tools left in the yard are ideal mosquito breeding sites.

Left in a corner of the yard these items can breed generations of mosquitoes for years
Solutions:
Rain Gutters
Rain gutters are one of the most overlooked spots for standing water in yards.
Most people don't check their gutters regularly.
The more tall trees you have around your house, the more likely it is you have clogged gutters...
Solutions:
I did an exhaustive test of just about every gutter guard design. I discovered that almost all of them fail...
Source: The Washington Post.
Tim Carter
Ask The Builder
There is type of gutter guard Tim Carter from Ask the Builder found effective...
But it was so expensive it would be cheaper to hire a handy man several times a year in most cases.
What if You Still Have Mosquitoes?
Getting rid of standing water will stop mosquito breeding in your yard...
But you can only take care of YOUR yard.
When it comes to neighbors and public areas around your home... If they aren't focused on preventing mosquitoes, they can be the reason for your next bite.
This is when stopping mosquitoes gets more complicated.... and layering effective strategies is your best best.